English Reference
noun · verb

decay

n. · v.
US /dɪˈkeɪ/ UK /dɪkˈeɪ/ de·cay UK spelling decays

  1. 01 B2 Upper Intermediate Biology

    n.the natural process of organic things, like food or wood, breaking down and rotting.

    n.the process or result of organic matter being decomposed, typically by microbial or fungal action.

    Simple

    The old log was covered in moss and showed signs of advanced decay.

    In context

    Forensic investigators used the rate of organic decay to estimate the time of death with surprising accuracy.

    decompositionrotputrefaction
  2. 02 B2 Upper Intermediate

    n.a gradual loss of strength, beauty, or health in a person, building, or society.

    n.a gradual deterioration in condition, status, quality, or strength.

    Simple

    The mayor promised to fix the urban decay in the city's oldest neighbourhoods.

    In context

    The historian argued that the empire's collapse was caused by centuries of internal moral and economic decay.

  3. 03 C1 Advanced Technical Physics

    n.the process where an atom loses energy by releasing radiation.

    n.the spontaneous transformation of an unstable atomic nucleus into a lighter one, accompanied by the emission of radiation.

    Simple

    Scientists measured the radioactive decay of the carbon to find the age of the bone.

    In context

    The half-life of an isotope is defined as the time required for half of the nuclei in a sample to undergo radioactive decay.

  4. 04 B2 Upper Intermediate Biology

    v.to break down naturally or go bad.

    v.to undergo decomposition; to rot through natural chemical or biological processes.

    Simple

    Sugar can cause your teeth to decay if you do not brush them regularly.

    In context

    Without proper ventilation, the wooden beams in the basement will eventually decay due to the high humidity.

  5. 05 B2 Upper Intermediate

    v.to slowly become weaker or lose quality.

    v.to decline gradually from a sound or prosperous condition to a lower state.

    Simple

    The relationship began to decay after they stopped talking to each other.

    In context

    The abandoned mansion was left to decay, its once-grand ballroom now filled with dust and shadows.

  6. 06 C2 Proficiency Technical Computing

    v.when a list of data changes into a simpler pointer in computer code.

    v.the process by which an array loses its type and dimensions, being reduced to a pointer, typically when passed to a function.

    Simple

    In C++, you must be careful when an array decays into a pointer.

    In context

    The developer noted that the array would decay upon being passed to the legacy function, losing its size information in the process.

    Usage

    The verb is intransitive in this context.

We see recently dead birds, who will be part of a feast for humans, and grapes that will soon either be eaten or will decay.

The Guardian· 7 Aug 2026
This entry
Level B2 · Upper Intermediate
Frequency Frequent
Updated